Method of and apparatus for obtaining dynamic balance.



N. W. AKIMOFF. METHOD OF AND APPARATUS FOR OBTAINING DYNAMIC BALANCE.APPLICATION FILED JUNE 5. 1915. RENEWED JULY 6. 1918.

1,296,605. E Patented Mar. 11,1919.

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METHOD OF AND APPARATUS FOR OBTAINING DYNAMIC BALANCE.

APPLICATION FlLEDl-l-JNE5,19I5- RENEWED JULY 6.19i8.

1,296,605. Patented Mar. 11, 1919.

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METHOD OF AND APPARATUS FOR OBTAINING DYNAMIC BALANCE. APPLICATION FILEDJUNE 5.1915IRENEWED JULY 6. I918.

1,296,605. Patentd Mar. 11,1919.

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1 UNITED STATES PATENT oEEIoE.

NICHOLAS W. AKIMOFF, OF PHILADELPHIA, PENNSYLVANIA, ASSIGNOR, BY MESNEASSIGNMENTS, TO DYNAMIC BALANCING MACHINE COMPANY, OF PHILADELPHIA,

PENNSYLVANIA.

METHOD OF AND APPARATUS FOR OBTAINING DYNAMIC BALANCE.

Specification of Letters Patent.

Patented Mar. 11, 1919-.

Application filed June 5. 1915. Serial No. 32,296. Renewed July 6, 1918.Serial No. 243,697.

7 '0 all whom it may on/W11:

Be it known that I, NICHOLAS W. AKI- M'HFF, a subject of the Czar ofRussia, and a resident of the city of Philadelphia, county ofPhiladelphia, and State of Pennsylvania. U. S. A., have invented certainnew and useful Improvements in Methods of and Apparatus for ObtaininDynamic Balance, of.

which the following is a full, clear, and exact description.

In the mechanical arts there are innuinerable instances of mechanisms.01' parts thereof, which, even when made with the reatest care byskilled mechanics employ- 1n the most accurate methods known to sclence,exhibit a tendency to vibrate when rotated at high angular velocities.This is generally apparent to a greater or less degree in such objectsas fly-wheels, crank shafts of internal combustion engines, and rotorsof steam turbines, as well as in many forms of electrical apparatus,etc.

Practice, as Well as theory, proves the absolute necessity of theexistence of a perfect balance constantly maintained in rotatablebodies, designed for relatively high speeds, both while stationary andwhile revolving at high angular velocities. The condition of beinbalanced while standing is termed statlc balance, and that while movingis known as dynamic, or running balance. The absence of a perfectdynamic balance causes a vibration of a rotating body, which vibrationupon being communicated to the allied mechanisms, bearings, andfoundations thereof, usually lessens the efiiciency of the device,shortens its useful life, destroys the means employed to secure thedevice to its fundation. and upon not infrequent occasions prevents theinstallation of the affected mechanism, because of its certain effectupon neighboring bodies.

By static balance is expressed in a concisc phrase a condition in whichthe center of gravity of a body lies somewhere upon the axis ofrotation. This is readily obtained by the well-known method of placingthe rotatable body upon knife edges, or parallels, then observin anypendular movement or oscillation, w ich may develop as a result of alack of balance. and then removing material from the unduly heavyportion, or portions. The result obtained insures the coincidence of thecenter of gravity with the central axis of the body, which latter is inprobably every instance analogous to the axis of rotation.

By the phrase dynamic balance there is implied the condition in whichthe center of gravity of a body lies upon its axis of rotation, as inthe above case. but with the additionalcondition of the axis of rotationof the body being coincident with one of its principal axe of inertia orof its momenta] ellipsoid; Such an essential condition is by no meansinsured simultaneously with the acquirement of a pcrfectstatic balance,and in fact has heretofore been exceedingly diflicult of attainment.

The object of the invention, therefore, is to provide a method, wherebythe quantitative effect of the one or more causes, such as air holes, orsuperfluity of material, preventing a perfect dynamic balance of arotating body, may be detected, their locations in angular directionanddistance from the axis of rotation functionally determined, and by asimple calculation an absolute remedy developed.

Another object is to provide a simple mechanism. embodying a thoroughlypractical adaptation or em 0 for universal employment in the mechanicalarts, wherein rotating bodies of unlimited shape and size are-employedand run at high speeds.

A further object is to provide a suitable mechanism, having one or morepairs of members parallel with, and adjustable longitudinally of, itsaxis of rotation, the entire mechanism possessing perfect dynamicbalance when all of said members'are in their respective neutralpositions, and the said mechanism being adaptable of association with adynamically unbalanced body, and operative by the shifting of saidmembers to indicate the position and extent of the ma diment of theinvention I terial causing the unbalanced condition of pairs, andwhilesaid device is revolving companying drawings in which, Figure-1 is aschematic view showing the usual method employed to determine theapproximate 10- cation of the cause of a lack of dynam c balance in arotatable member; Fig.l2'is a geometrical diagram, showlng therelatlonbetween the major axis ofthe momenta] elhpsoid of inertia of adynamically unbalanced body and the axis of rotation; Fig. 3 isan moun gof the'same, and Fig; 13 is amodi-el-fied form of the device applied toa rotatable e co elevation of a simple mechanism comprise Y ing-oneembodiment of the 1nvent1on;;F1g.

at is a diagrammaticfigure showingthe 'rela tion of the various factorsencountered and employed to readily determine the proper;

position and amount of material necessary to e removed from theunbalanced body," to. properly balancethe same g. '5 is;a frag-= mentarysectional' view of one. endjofthe squirrel cage, showing weight-controlling 1 mechanismsmounted uponIone'of-"the end: plates of thcage; Fig.-6'is an enlarged detail View of the same on the lineof'fFig'. 1

; Fig. 7 isafragmentary' detail view of a portion of the same; Fi 8is-a] section. on the line 88 of'Fig.'.7-; Fig-9 is an elevation of thesquirrel cage With'a modified .formof weight-operating means mounted:thereon'.

Fig. 10 isa section onthe line10"10 of- Fig. 9; Fig. 11' is av detail ofthe weight-shifting.

hollow body carriedfby a vertical axis;

, Referring to-Fig'. l, a representativebody 15 is shown, mounted torevolve' -1at high .l angular velocities upon "the axis of. rotation 16,passing through bearings 17 adapted 'to plane, said body v being drivenbyany zs'uitf yield "slightly tovibrations in ho able means, as by themotor. 18, jthrough th&

pulley 19, belt 20'Iand pulley' 21j 'Moun'ted in suitable supports (notshown) {is a set; of scribes 22 and 22", locatedupon-diametri-.

cally oppesitesides of the bodylvl5 and ad.-

jacent to'the surface thereof, as-indicatedgg "Said scribes arecarefully adjusted as the unbalancedifbody revolves-until; the latterencounters one or bothof, them duringa por-' tion of each revolution, asit reciprocates'in the yielding bearings 17, transversely. tothe axisvof rotation. [In this manner slight scratches arema-de upon the surfaceof the body showing so-called highgp ointsm' fromwhich there can bejudged something-0fthe approximateposition from which some ma-A terialshould be removed to properly balance the body dynam iea lly. liutthisfcan, in no way be made to indieate either the exact I position fromwhich said material should be removed, or the exact amount necessary, toaccomplish the desired result; Several tIlalS- are as a rule necessaryand then only a partial success is obtained.

With acondition such as'this case pre-' sents, it is readily possible tobalance the l body statically by meansof resting the same mounted on itsshaft'upon parallels, or knife edg s,vand then removing material asproves tobe neces'sary.'. Thus, for instance, a heav'y opposite-side ofsaid axis. This then in sures perfect static balance while SXR equals8X1. But this addition of compen sating' material being diflicult, anequal amount maybe removed from the same side of the axis of rotation asthe heavy spot S.

AlI thatis necessary is to select the best .ava1lable spot from which;such material [may be removed with safety 'to the resulting' structure,-measure the radial-distance 7- from the said axis, and solvetheabove'equaf tion for. a In-thismannerfa perfect st'andingbalanceisjinsured, but it isno guarantee that there will, not developheavy vibrations 'as" soon fas the body is revolved at highspeedsgfCertain centrifugal forces will ap pear, which will cause an-unduevibration of thewhole system, andlwhich can not be saltisfaetorilyovercome by ordinary qmethotsp v v H 1111 Fig; 2 is shown graphicallythe condi- 7 tions of unbalance and balance of. a revolvwing body. Inthefirst case, the ellipsoid of inertia A is symmetrical about'major andminor-axes B and G, which intersect at-a point-D, comprising "the centerofigravity of v in Fig. -Wh'en; the cause, or causes,- of unbalance are'removed "and a- State' of. perfect balance attained, the ellipsoidswings about the point D, "the a one point that remains fixed, llntjllit fassumesthe position E, in which position the axis B .is coincident"with the" I .1'15 It isito be noted that, in. rotating a body. "athighfspe'ed toldetermine whether or not it'possesses ,a' perfectbalance, several simple g devices of seismographic-nature may be e'm-'ployed, and-in this way the vibrations are recorded, thoughno-factor oftheir cause .indicated; However, it should be statedjthatthe bodyand-marked with an axis of rotation 16.

of vibrations in amechanism at a certain high speed does i'iot indicatea perfect dynamicfbalanc'e; there'is a speed called the,

critical speed? at which a body, I ven though lackingthe desiredbalance, will ro-.- Y I tate smoothly, which action is due to theperiodic; vibrations of its supports ,(ounter iio acting the vibrationsof the body. This critical velocity can not confuse or mislead one, forthe vibrations of the mechanism appear at the speed both above and belowthe same and in a given mechanism always disappear only at a definitecritical value. However, a body, which is balanced for any speeds exceptthe critical speed, is balanced for all speeds.

The simpliest embodiment of the invention is shown in Fig. 3, whereintwo, or

more, circular plate 25 are mounted securely upon a shaft 26, journaledin suitable rigid bearings 27, carried by a frame 28, said shaft beingprovided with a pulley 29 from which a belt 30 passes to a pulley 31upon, or driven by, a motor 32. A rotatable body 35 is mounted upon theshaft 26 and made to revolve therewith, said body having irregular,unbalanced portions 36, While between the plates 25 and passing shdablytherethrough is a plurallty of rods or weights 37, which may be securedin any given longitudinal position parallel with the axis of rotation bymeans of set screws38.

The plates 25 and longitudinally adjustable weights 37. when the latterare in their neutral positions and unassociated with an unbalanced body,form a perfectly balanced squirrel cage. the major axis of its ellipsoidof inertia being coincident with its axis of rotation. And, it isevident that any displacement of the two diametrically situated rods inopposite directions shifts the major axis of the ellipsoid of inertia ofthe cage out of coincidence with its axis of rotation. .For anexplanation of this fact, ref erence is made to Fig. 4.

If in order to establish a perfect dynamic balance, it is necessary todisplace each weight from its neutral position by the dis tance u, itcan readily be inferred that the centrifugal couple thus createdi's2mm,- this was the displacement found to be necessary to counterbalancethe original centrifugal couple, which caused an unbalanced condition ofthe systetn, comprisin the balanced cage and unbalanced body within, dueto the over dense regions S and in the material comprising the body.

The centrifugal couple due to the latter is 'SXRXZ, or .s-Xr-Xz; S and.s' being the masses, so far unknown. and SR being equal to 87' in Viewof the initial condition of static balance. Therefore, 210/17 equalsSRZ. whence can be readily determined either of the elements, byassuming for practical reasons, the remaining twofor instance, if it ispreferred to drill in two opposite places S and 8, Z inches apart, then,selecting the radius R, the amount to be removed at S is readilydetermined. And, inversely, material should be removed from points suchas S and '8 upon opposite sides of the axis, since RS equals as, (fromthe hypothetical condition of a static balance) ,the solution oftheproblem presented becoming perfectly definite.

Inasmuch as the adjustment of the Weights shown in Fig. 3 requiresfrequent starting and stopping of the system, which may beobjectionable, the movable weights of the system have been provided withmeans to control or shift the same while in actual rapid motion, withthe result that it is not necessary to stop the motion of the systemuntil the correct positions of the balancing rods have been determined.This can be readily accomplished by such mechanism as that shown inFigs. 5 to 8, inclusive.

In this instance one of the plates 25 is provided preferably withelectrically operated, reversible motors'42, in number sufficient tooperate the respective-pairs of oppositely situated rods or weights 37.Each of the shafts of said motors is provided with a worm Wheel 43.which meshes with a worm gear 44, carried by a shaft 45, journaled inbearings 46, and provided in turn at its opposite ends with gears 47,operative to mesh with gears 48, carried by shafts 48 and 48", in turnprovided with worms 48, meshing with worm gears 48.

Said worm gears 48 are suitably mounted in a fixed position with respectto the neighboring plate25 and are provided with central apertures 50,the surface of said apertures being spirally threaded and adapted toengage the teeth of racks 51, secured to and forming unitary parts ofsaid rods or weights 37 The two worms 48 carried by each of the shafts48 and 48 are respectively right and left handed, so that, as a motorrevolves in a given direction, the weights shlfted thereby are moved inopposite directions through the end plates of the cage, and a reversalof said motor reverses the directions in which said plates are moved. Bytheconstructions and relative positions of the various elements of thedevice as shown in Fig. 5, the dynamiccbalance of the structure ismaintained.

Referring now to Figs. 9 to 12, inclusive,

a modified form of the' device is shown as comprising the end plates 55,connected by rods 56, fixed with respect thereto, and providedrespectively with dove-tail grooves 57, in which are slidably mountedlongitudi nally movable weights 58, provided in turn with rack teeth 59.Surrounding and secured to each of said rods are spaced collars- 60,having integral, radially extended flanges are provided, substantiallyas shown in Ifig. 10, for the purpose of directin fluid ets against thevanes of said whee s 64, flu d being supplied to said nozzles from asultable source under hi h ressure through the pipe 70, two-way val ve$1, and pipes 72 and 73. For instance, to shift the upper weight awayfrom, and the lower weight toward, the sheet, the valve handle 7 1 maybe turned upwardly permitting fluid'to pass through the pipe 72 andadjacent nozzle to the oppositely positioned vane wheels, as they flypast upon the rapidly revolving cage. And, to reverse the movement ofsaid weights, fluid is cut ofl from the pipe 72 and sent through thepipe 73 with the result desired,

no fluid escaping through either of said nozzles when the valve handleis in the position shown.

As the great number of rotatable bodies is not limited' to those havinghorizontal axes of rotation, as for instance cream separator bowls, orextractors which revolve upon vertical axes, Fig. 13 shows a simpleadaptation of the invention to'the balancing of such a body. In thiscase any representative bowl 80 is shown, as revoluble upon a verticalaxis 81, which also carries spaced platforms 82, between which and uponone is located a suitable motor 83, or other actuating mechanism,operative to drive a shaft 84, provided with worms 85, in turn operativeto mesh with and revolve worm wheels 86. The .turning of said last-namedwheels operates the vertically extending parallel rods or weights 87 ashereinbefore disclosed. While this last embodiment of the invention isbut briefly described, it is intended to clearly show the efii'cientadaptation of. the inventionto rotatable bodies of this character,namely, those revoluble upon other than horizontal axes. I

It has furthermore been shown that, with the embodiments of theinventionhereinbefore described, it is ssible, while the system isrevolving rapidly, to readily and in a very short time, adjust themovable v weights, show that the dynamic balance of the system isattained, after which the samemay bestopped and the amount of materialtobe removed readily ascertained with both certainty and ease.-

Having thus described my invention, what I claim and desire to protectby Letters Pat-- ent of the United States is 1. A system, rotatableabout an axis fixed within said system, said system comprising a bodyprovided with adjustable Weights, means cooperating with said weightsand adapted to adjust the same during the rotation of said system, toalter the position of the principal axis of inertia of said bodyrelative to the direction of the axis of rotation of the system.

2. A system, rotatable about an axis fixed within said system, saidsystem comprising a body provided with adjustable Weights and adapted tobe revolubly associated with a body to be tested, means cooperating withsaid weights and adapted to adjust thesamc, to alter the position of theprincipal axis of inertia of said first body relative to the directionof the axis of rotation of the system,

to counterbalance the relative difference be-,

tween the axis'of inertia of said body to be tested and the axis ofrotation of said system, and to make one of the principal axes ofinertia of the system coincident with the axis of rotation of saidsystem.

4:. The combination of two bodies rotata-v ble about a fixed axispassing through the centers of mass of said bodies, and adjustableweights carried by one of said, bodies and operative to shift theprincipal axis of inertia thereof into coincidence'with the axis ofrotation of the system.

5. The combination of a body adapted to be revolubly associated with abody to be tested and the latter being rotatable about an axis passingthrough its center of mass, and adjustable weights carried by said firstbody and creating a centrifugal couple, operativeto neutralize acentrifugal couple of said second body, said bodies [being connected andhaving, their centers of mass located upon the common axis of rotation.

6. The combination of a body adapted to be revolubly associated with a.body to be tested and the latter being rota-tablea-bout 1 an axispassing through its center of mass;

and adjustable. weights'carried by said first v gal couple of body andcreating a centrifugal couple, erative-to neutralize a centrif saidsecond body.

7. The combination of a body adapted to be revolubly associated with abody to be tested and the latter being rotatable about an axis passingthrough its center of-mas s. and adjustable weights carried by saidfirst body and creating a centrifugal couple, op-

erative to neutralize a centrifugal couple of said second body, saidbodies being connected and having their centers of mass located upon thecommon axis of rotation.

8. A dynamic balancing mechanism, comprising an adjustable systemrotatable about an axis passing'through its center of mass,

and adjustable means forming a part of said system and operative to tiltthe principal axis of inertia of the combination into coincidence withthe axis of rotation While said system is rotating.

9. A dynamic balancing mechanism, comprising a dynamically perfectlybalanced system adapted to be revolubly associated with a body to betested, adjustable means operative to create an unbalanced condition ofsaid system, to counteract and neutralize the extent of the unbalancedcondition of said body to be tested, and means to control saidadjustable means while said adjustable means is revolving.

10. In a dynamic balancing machine, a system comprising means adapted toreceive a body to be tested, both said system and said body when inposition beingrotatable about a common ax1s passing through theirrespective centers of mass, weights movable in said system parallel withthe axis of rotation thereof, and means operative to shift said weightswhile said machine is in operation.

11. In a dynamic balancing machine, a system comprising means adapted toreceive a body to be tested, both said system and said body when inposition being rotatable about a common axis passing through theirrespective centers of mass, airs of weights movable in oppositedirections in said system with respect to the center of mass of saidsystem and parallel with the axis of rotation thereof, and meansoperative to shift said weights while said machine is in operation.

12. A dynamicbalancing device, comprising a revoluble squirrel cageframe, the longitudinal bars of which are independently adjustable andmeans to move said bar while said frame is in motion.

13. A dynamic balancing device, consisting of a revoluble frame,comprising oppositely disposed members, parallel, independently adustable members extending therebetween, and! means to adjust saidlastnamed members while said frame is revolving.

14. A dynamic balancing device, comprisspaced parallel plates, andspaced parallel :bars extending between said; plates movableindependently of one another and means to affect a shifting of said barswith respect to said plates while the same are revolving.

15. A dynamic balancing device, comprising spaced parallel plates,spaced parallel bars passing slidably through, and extending between theperipheral portions of said plates and movable independently of oneanother, and means to simultaneously adjust a plurality of said barswhile the device is revolting.

16. A dynamic balancing device, comprising spaced, parallel, centrallyapertured plates, a shaft passing through said apertures, equally spacedparallel bars extending between said plates, longitudinally adj ustablewith respect thereto, and independently of one another, and means toshift said bars longitudinally while the device is in motion.

c 17. In a device for obtaining dynamic balance, a squirrel cage frame,having longitudlnally adjustable parallel bars, a shaft upon which saidframe revolves, and means shaft are revolving.

18. In a device for obtaining dynamic balance, a. shaft, spaced parallelplates u on sald shaft, spaced parallel bars passing s idably throughsaid plates, and means couphngthe diametrically opposite of said bars inpairs, and operative to adjust the longitudinal positions of the bars ineach of said respective pairs simultaneously.

19. In a device for obtaining dynamic balance, a shaft, spaced parallelplates upon said shaft, spaced parallel bars slidably through saidplates, and electrically op erated means carried by said plates andoperative to simultaneously adjust the bars in each of the respectivepairs of diametrically opposite bars in opposite directions.

20. The method which consists in associating a dynamically unbalancedbody with a body adapted to be perfectly balanced dynamically so thatthe tWo may be revolved synchronously, thus forming a dynamicallyunbalanced system, and then unbalancing said last-named body while saidsystem is in motion, to neutralize the unbalanced condition of saidfirst body to balance said system.

21. The method which consists in associating a dynamically unbalancedbody with a body adapted to be perfectly balanced dynamically andoperative to indicate the condition of dynamic balance of the. systemthus formed, so that the two may be revolved synchronously, thenunbalancing said second body to neutralize the unbalanced condition ofsaid first body, to balance the system while the same is rotating, andfinally removing'material from regions of said first body in ratios ofpositions and amounts as indicated by said second body.

22. In a dynamic balancing machine, a system comprising means adapted tobe associated with a body to be tested, means whereby both said systemand'said body are adapted for rotation about a common axis passingthrough their respective centers of mass, said system comprising weightsmovable therein parallel with the axis of roto adjust said bars whilesaid frame and j 7 whereby both said system and said body are adaptedfor rotation about a "common;

axis passing through their respective cen-' 'ters of mass, said systemcomprising pairs of Wei hts movable thereinparallel with the Y axisrotation thereof and 'in opposite 'diable therein fp tation thereo temis in rotation."

24. In a .dynamic'balancing ma'chiiiefa 1. system comprising 'sociatedwith ation.

sociated with a body .to be tested, means adapted for rotation. about, acommon axis passing through their respective centers of mass, saidsystem comprising pairs, of

weights movable therein parallelwithfthc f axis of rotation thereof andin oppositedi---. rections,"and means operative to. shift. said weightswhile said system is in rotation.-

its dynamic balance, said mechanism! com prising a structure adaptedtorota'tably hold a body to. be tested, means for mountlng 'sa1dstructure to rotate, upon an; axis concentric systemjconsisting of saidstructure and said' with said body, said structure including: ad-

justable means for altering. the momental ellipsoid of the systemconsisting-.of'said structure-and said body, and means for ,effectingsaidadjustment during the rotatlon of'said system.

. for mounting said structure to-rotatev upon 1 an axis in a plane withthe axis of said body, said structure including adjustable means foraltering the-momental ellipsoid of the I 1 body, and means for effectingsaid adjust- 3 lubly associating so as to form a rotatable system, adynamically unbalanced body with a a body capable of being adjusted topossess ,ment, during the rotation of saidv system. 28, The method whichconsists in 'revo-.

perfect balance, and operative to indicatethe condition of balance ofthe system thus formed, and then unbalancing said last-f named bodywhile said system is in motion to' neutralize the unbalanced conditionof; said first body and to balancefthe system.-

v 25. In a dynamic 'balancing'machinda; system comprising 'means adaptedto be as said system.

prising the combination of a set of weights,

means operative to support said weights, and

means to revolve said supporting means'and means-to move said weights tocause their p planes1of.' rotation to move with respect to IGCtIOIIS,and electrically operated means operative to shift said weights while.said sys j said-.zsupporting means.

1 A dynamic-balancing machine, comfprisin githecombination-of a set ofweights, means adapted to beas-I- to rotate said weights in parallelplanes, and

means'operative to' support said weights, and

means to revolve said-supporting means and t to rotate-said weights inparallel planes, and gmeans move said weights to ,cause their planes "ofrotation to move with respect to one another longitudinally 'of the axisof sald j'snpportlng means while said weights are-"in motion. v

31.' -A dynamic balancing machine, com-- prising the combination. of apair ofweights," I means operative to support said. weights, means torevolve said supporting means and to rotate', said weights 1n. parallelplanes about the axis 'ofr'evolution of said supporting means, andmeans-operative to alter the relative positions of said the weights soas to shiftjqsaid parallel planes with respect to .eachother andlongitudinally of said axis.

32; A dynamic balancin machine, comprisingthe combination 0 a'"pluralityof t pairs of -weights,.means operative to' support 26. Amechanism for testing abodyas to said-weights, means to revolvesaidsupport:

- ing means and1t'o.rotate said weights in par al'lel planes abouttheax'is ofsaid supporting means and weightsare in motion. f v

' 33, The method. which consists in mechanically associating adynamically unbalanced Y .7 "body witha body; adapted to be perfectly 27A'mechanism for testing a-.body-asfto.v its dynamic balance, saidmechanism com- I prising'a structure adapted to be vrotatably associatedwith. a body to be tested, 'meanSI.

balancedand] unbalanced dynamically at enc'y of-theother to vibrate 1funbalanced and'so that the ,twoimayfberevolved synchronously,.thusforming a. dynamically un- 34. A dynamic. balancing machine, Icomij balanced's -s tem,and then unbalancin'g said last-name bodytoneutralize the unbal:

1 anced condition of'sai'difirst body to balance in prising'a supportforabody to be tested, and

1 a balancing unit connected to and revoluble .insynchronism-with saidsupport. and consisting of a plurality of equal weights revo-' luble inparallel planes movable with respect to each other. v v

35. A Qdynamicbalancing machine, comprising a support for-a body to be;tested,

anda balancing unit connected to and revoluble insynchronism with saidsupport-and sisting of a. plurality. of equal weights revoluble inparallel planes movable with respect to each other while said weightsare in motion.

36. A mechanism for testing a body as to its dynamic balance, saidmechanism comprising a structure adapted to rotatably support a body tobe tested, means for mounting a second structure to rotate upon an axisconcentric with said body and adjustable longitudinally with respect to.said first structure, sald structures including means equal in weightfor altering the momental ellipsoid of inertia of the s stem consistingof said structures and said ody, and means for efl'ectin said adjustmentduring the ro tation of said system.

37. The method which consists in mechania.

cally associating a dynamically unbalanced body with a body adapted tobemperiectly balanced and unbalanced dynamically at will so that the twomay be revolved synchronously, and so that, when so revolved, each tendsto oppose the tendency of the other to vibrate if unbalanced, thusforming a dynamically unbalanced system, revolving said system todetermine its degree of unbalance and then unbalancing said lastnamedbody to neutralize the unbalanced condition of said first body tobalance said system.

In witness whereof, I have hereunto set my hand this 4th day of June,1915.

NICHOLAS W. AKIMOFF. Witnesses:

N. O. FREEMAN, J. STUART FREEMAN.

